Lavoy is correct, originally the venturi fits tightly. I believe over time the venturi relaxes and loses the tight fit, that is why I used the sealer and it cured my problem. I believe the venturi is aluminum or pot metal while the carburetor body is cast iron.

They should be brass, but have seen some plastic or synthetic ones on occasion.
I have been replying to your PM's, must not be getting them. Shoot me an e-mail at postmaster@jdcrawlers.com instead.
Lavoy

Parts and restoration for antique and late model John Deere crawlers.
Owner and moderator www.jdcrawlers.com

Update - rebuilt the carb installing all new parts from a carb kit but still have the same problem. If I ever figure this thing out I'll let everyone know. Leaning towards replacing the carb if I can find one. Wish me luck!

UPDATE - replaced the carb with a rebuilt and my dozer runs like a charm! Tried it out by pushing out a pine stump from a tree that had blown over from a storm this summer and it didn't hesitate one bit. I had even sprayed some paint on the machine to make it look pretty.

I had that problem with a 420 C, even had the carburetor rebuilt and problem persisted. I finally took carburetor apart and took an air chuck with a rubber tip so I would get somewhat of a seal and blew through all holes, especially all of the small ones. Some are barely larger than a pin. Problem solved, the tractor idles smooth without using choke.

I'm guessing you didn't find all the holes in the load jet Lavoy mentioned. They can get so completely filled in that they no longer exist, and you have to shine it up to see where there are dark spots instead of brass.